Title: Fast Beam Diagnostics at the ILC Using the Beam Calorimeter
1Fast Beam Diagnostics at the ILC Using the Beam
Calorimeter
- Christian Grah, Desy
- FCAL Workshop
- 12-13 February
- Cracow
2Contents
- Very forward region and BeamCal
- Beam parameter reconstruction
- Principle
- Results on 20mrad geometry with the nominal ILC
parameter set. - Summary and outlook
3Very Forward Region
- LumiCal 26 lt ? lt 82 mrad
BeamCal 4 lt ? lt 28 mrad
- PhotoCal 100 lt ? lt 400 µrad
4BeamCal
ee- pairs from beamstrahlung are deflected
into the BeamCal
Deposited energy from pairs at z 365 (no
B-field)
- 15000 ee- per BX gt 10 20 TeV
- 10 MGy per year
- fast gt
O(µs) - Direct photons for q lt 400 mrad (PhotoCal)
Wdiamond sandwich calorimeter
5Backgrounds (Old 20mrad Geometry)
Sketch of old BeamCal geometry.
Projection of LumiCals inner radius.
Energy deposited in LumiCal from pairs.
6ILC B-Field Configurations
20mrad DID (Ri(LumiCal) 13.5cm) (Ro(BeamCal)
16.5cm)
20mrad AntiDID (14mrad seems necessary for
AntiDID)
An AntiDID configuration is close to the
headon/2mrad design. BUT better be prepared for
both possibilities.
DID Detector integrated Dipole, B-field aligned
with the incoming beam AntiDID B-field aligned
with the outgoing beam
7Fast Luminosity Monitoring
- Why we need a fast signal from the BeamCal?
- We can significantly improve L!
- e.g. include number of pairs hitting BeamCal in
the feedback system
Improves L by more than 12 (500GeV)!
position and angle scan
G.White QMUL/SLAC RHUL Snowmass presentation
Luminosity development during first 600 bunches
of a bunch-train. Ltotal L(1-600)
L(550600)(2820-600)/50
8Beamstrahlung Pair Analysis
- A lot of information is stored in the energy
distribution of beamstrahlung pairs hitting
BeamCal.
- Observables (examples)
- total energy
- first radial moment
- thrust value
- angular spread
- E(ring 4) / Etot
- E / N
- l/r, u/d, f/b asymmetries
- Beam parameters
- sx, sy, sz and ?sx, ?sy, ?sz
- xoffset
- yoffset
- ?x offset
- ?y offset
- x-waist shift
- y-waist shift
- Bunch rotation
- N particles/bunch
- (Banana shape)
detector realistic segmentation, ideal
resolution, bunch by bunch resolution
9Analysis Concept
- Beam Parameters
- determine collision
- creation of beamstr.
- creation of ee- pairs
- guinea-pig
- (D.Schulte)
- Observables
- characterize energy distributions in detectors
- FORTRAN
- analysis program (A.Stahl)
- and/or
- GEANT4
1st order Taylor-Exp.
Solve by matrix inversion (Moore-Penrose Inverse)
10Coefficients of the Taylor-Matrix
observable j au
beam parameter i au
11Analysis for nominal ILC Parameters
single parameter analysis
Quantity Nominal Value Precision Precision
old new
sx 553 nm 4.8 2.9
?sx 3.9 7.4
sy 5.0 nm 0.1 0.2
?sy 0.1 0.4
sz 300 mm 8.5 8.5
?sz 6.7 6.3
Dy 0 2.0 0.6
ILCNOM, 20mrad DID
122mrad and 20mrad Analysis
Quantity Nominal Value Precision Precision
2mrad 20mrad 20mrad (2par)
sx 553 nm 3.1 2.9 2.8
?sx 5.2 7.4 7.6
sy 5.0 nm 0.3 0.2 0.2
?sy 0.3 0.4 0.4
sz 300 mm 4.8 8.5 11.1
?sz 3.7 6.3 7.4
ey 40x10-9mrad 1.7 2.9 5.2
ey 0 4.2 4.1 4.7
Dx 17.7 9.3 10
Dy 0 0.5 0.6 0.6
N 2x1010 0.01 0.01 0.01
DN 0 0.01 0.02 0.03
...
13Status of Analysis
- GuineaPig files for ILCNOM ready (400 pair
files). - New geometry ready.
- Single and multiparameter analysis started.
Mostly done for - 2mrad
- 20mrad DID
- Good progress in the Geant4 implementation
(A.Sapronovs talk).
14Summary Outlook
- Including a fast signal of number of pairs or
total energy into the feedback system can
significantly increase luminosity of the
accelerator. - Analyzing the spatial energy distribution of
beamstrahlung pairs hitting the BeamCal grants
access to many beam parameters. For highly
correlated parameters measurements from other
systems can be included (e.g. PhotoCal). - 20mrad geometry is implemented with DID field
approximation. - ILCNOM investigation is in work.
- Geant4 simulation is running, BC observable
calculation and beam parameter reconstruction can
be done with some limitations. Next - Geant4 simulation with realistic b-field map and
compare to simplified one. - Hopefully no fast shower simulation has to be
included (cpu time dependent). Fast shower
simulation is implemented in Geant4 for
homogenous detector. - Find most interesting regions (layers) in the
BeamCal segments. - Need background calculation for our 20mrad
geometry.